Lens



June 19, 1923. 1,459,373

7 M. A. LAABS LENS Filed Jan! 12, 1921 INVENTOR MAX A. LAABS ATTORNEYS Patenteddune l9, 11%23.

stair Iaax arrano Lanes, or soornnnrnea. MASSACHUSETTS, sears-non 'ro arena-roan orrrcat semester, or sournsnrner, massacrruswrrs, a vorunraar A$CM- TION @F MAESACHUSETTS.

Application filed January 12, 1921. serial Ito. 6,669.

T all whom it may concern;

Be it known that I, Man A. Lanes, a citizen of the United States, residing at South.- brid e, in the county of Worcester and State of l -lassachusetts, have invented certain new and useful Improvements in lenses, of which the followin is a specification,

This invention re ates to improvements in lenses and has particular reference ll11-= 19 proved form of blank for multiiocai lens, @ne of the leading objects of the present invention is the provision of commercial leak or article of manufacture to be sub sequently transformed into a multii ocal lens formed from two or more portions of glass which shall he so constructed that the comhined focal values of the two portions of glass may he readily determined before the lens has been surfaced. V

A further object of the present invention is the provision of a novel and improved blank for a inultifocal lens which shall he so constructed that the portion of the lens of greater power may be readily examined prior to the surfacing operation, thus eliminating the grindin up of defective blanks, and in which in a dition the power of said portion ma be measured upon the surface in place '0 through neutralization as has hitherto been necessary.

A further object of the invention is the provision as an improved commercial artido of a lens blank which shall be composed of a major portion havin a countersink and a segment disposed witnin the countersink so constructed that there will he an absence of power in the blank through the segment and countersink, enabling; the efiec tive additive value produced through the countersink and segment construction to be {measured upon the exterior surface of the ens.

Other objects and advantages of my improved construction should be readily aparcnt by reference to the following specication taken in connection with the ac companying drawings, and it will be understood that I may make any modifications in the specific details of construction'shown and described within the scope of the ap pended claims without departing from or exceeding the spirit of my invention.

Figure 1 represents a plan view of a blank embodying my improvements Figure ll represents a sectional view as on the line li-ll illustrating one step in the formation of the same. s

Figure 1H represents a similar view illus trating a further step.

Figure IV represents a view similar to Figure ll of anaeniscus form of lens.

Fi ure V is a view corresponding to Fig are ill of the same form of lens, and

Figure VI illustrates a finished lens manufactured from such blanks.

Prior to my invention it has been custernary to manufacture what is known as two-part bifocals, multifocals, or the like through the use of a major disc or slab 1 having a recess or countersink 2 formed therein to receive the segment portion 3 formed of a glass of a different index of refraction. This segment portion may he secured in position in the countersink either through fusion or through the use of a suit able cement orv uniting medium. in either event the result is the same; that is, av lens having a plurality of different fool is pro vided when the blank is surfaced on the two sides, one focus being the result of the exterior curves on the two faces of the glass and the other focus being the result of the four curves; that is to say, of the two surface curves and the two united inner curves combined with the difiereuces in index of refraction of the two glasses. 'l his difi'er-. once it has always been impossible to measure in the lens through the process of neutralizing. This on the other hand is re quired that the last surfaces be rendered clear or transparent either through grinding and polishing or through the use of cover glasses, enclosed films and the like. In any event, however, the determination of the power ol this portionof the lens has been dependent entirely on proper neutralization before grinding while inspection of the surface has also been rather difficult .with the result that in many instances work has been wasted in grinding up a lens which was afterwards found to be defective in the countersink portion or one in which the countersink did not give the desired additive result in the finished lens.

These lenses it is to be understood are ordinarily sold in what is termed blanks; that is to say, in a fiat or curved slab having the segment secured in position thereon so that the bifocal part or addition is completed but requiring grindin on one or both sides, Figures II and l. therefore, illustrating the commonly known form of commercial blank as generally produced b the manufacturer and sold to the trade. t is to this that my improvement relates. My,

' improvement consists in a new process of jor partion 1 as having formed therein the countersink having a power as respects the crown of about 19.50 dloptres, while secured within the countersink is the flint button or segment 3 having its lower face fitting and secured in position within the countersink. Ordinarily, this button would have a substantially fiat upper face producing an additive value due to the difference in refraction of about 3.50 dioptres, or in other words, the lens illustrated, being a flat or plano blank, would have a zero power in the distance portion and a +3.50 power in the reading portion. In my process I then form on the upper face 4: of the segment a curve of such power as to counteract or neutralize the power produced by the counterproduce a wwer of about 3.50 dioptres,

sink so that the lens will have no power through the countersink, this curve being formed, however, on the countersink only and not afiecting the major portion of the blank in the slightest, nor deep enough to interfere with whatever curve, either concave or convex, it may be desired subsequently to form on the bifocal face of the blank. in the example just quoted I would form on the segment 3 a curves: which as respects the crown glassot the major portion would produce a power of approximately 3 dioptres but which on the higher index flint will thus counteracting the +3.50 dioptre ower produced through the countersink va we of 19.50 dioptres.

ing one local v as an resents and polished surface on the countersink or segment or button, and preferably having a cleared on-transparent back surface as at 5, it will be possible to look directly through the countersink and determine Whether there is any appreciable amount of residual power left after the application of the neutralizing curve thereto. In addition there will be no power in the countersink, and it will be possible to examine it as a plain piece of glass and to locate any defects due to pebbles, poor fusion, color or the like. It will also be possible through measuring the curve 4: and determining the ratio power of flint lens produced by that curve, algebraically adding the curve on the face 5 and crown power produced by that curve, to determine 'by surface measurement of the blank just what the additive value is through the countersink'or segment portion of the lens. This is the first time in the manufacture of lenses of this character that it has been possible in measure mechanically and detercave curve and the other part having a, portion fittingsaid curve, the segment and major portion being of glasses of-idifierent index of refraction, and the segment having a curve on its exposed face neutralizing the addition produced in the lens due to d-ifi'er-' ence in index oil: refraction of the parts.

2. A blank for a multifocal lens compris ing a major portion having a countersink formed from glass of one index of refraction and ase ent in the countersink formed from-glass with a difl'erent index of refraction, said segment having on its exposed face a curve neutralizing the additive value present due to diderence in index of refraction of the two glames.

3. A lens formed from a plurality of portions of glass having diflerent indexes of refraction, having curved joining faces produring an additive value through portions of the blank, and having related curved exerior faces counteracting said additive elect. I

4:. A lens com rising a major portion hava minor portion havmg a difierent focal value, and a segment secured to and overlying the minor portion,

emme the faces of the segment being related to produce a, power which Will neutralize the produce power sufficient to neutralize the power of the lens through the countersink. focal value of the minor portion. In testimony whereof I have afiixed my 5. A multifocal lens including a major signature, in presence of two witnesses.

5 portion having a countersink formed therein MAX ALFRED LAABS. and a segment of different index of refrac- Witnesses: Y tion from the major portion overlying the Anion G. HEAASKELL,

. AFLER.

countersink and having its faws related to Es'rw M 

